Singapore Technologies Engineering is buying the aviation business in a bid to "scale up" its own aerospace capabilities. Middle River Aircraft Systems employs about 800 people and has designed and built aircraft for almost 90 years.

The $630 million price is subject to change based on certain factors, including GE'sunderfunded pension obligations. After years of inattention and historically low interest rates, GE(GE) has built up the biggest pension shortfall in the S&P 500.

And GE has previously sold off its appliance division, the media giant NBCUniversal and much of the giant bank known as GE Capital.

But until now,GE hasn't moved to shrink its booming aviation business.

GE Aviation is the most exciting part of the renovated company. Its technology powers two out of every three commercial flight departures around the world. And GE Aviation sports a decades-long backlog of orders totaling around $200 billion.

Wall Street is hoping GE's jet engine business will lift the rest of the company out of the doldrums. The remnants of GE Capital — especially insurance and a defunct subprime mortgage company — continue to suck billions out of the parent company. Last month, GE agreed to sell its energy debt financing business to Starwood Property Trust(STWD) for $2.6 billion.

GE is holding on toits renewable energy division, which features a large onshore wind business. However, renewable energy remains a tiny part of the company's overall sales.

And GE Power, which makes power plants, has been slammed by the shift away from fossil fuels. GE has been laying off workers and shrinking its footprint. Last month, Bloomberg News reported that GE is also preparing to sell its power conversion business for about $1.5 billion -- or less than half it paid for the business in 2011.